Field of the Invention
Embodiments of the present invention generally relate to a method for bonding substrates and components suitable for use in a semiconductor processing chamber fabricated by the same, using a segmented bond design.
Description of the Related Art
In substrate processing applications, many chamber parts and components are fabricated using two or more parts, or substrates, bonded together. Examples of such components includes electrostatic pucks bonded to temperature control supports, showerheads bonded to gas distribution plates, and heaters bonded to chamber lids, among others.
FIG. 1 is an example of a conventional chamber part comprising substrates bonded together illustrated as an electrostatic chuck assembly 100. The electrostatic chuck assembly 100 includes an electrostatic puck 102 coupled to a temperature control base 106 by an adhesive layer 104. The electrostatic puck 102 includes a substrate support surface 120 on which a wafer (not shown) is electrostatically retained during vacuum processing. The substrate support surface 120 generally includes a plurality of backside gas delivery holes (not shown) to provide a backside gas, such as helium, to improve heat transfer between the substrate and the electrostatic puck 102.
The adhesive layer 104 is generally a continuous monolithic layer that covers the entire mating surfaces of the electrostatic puck 102 and the temperature control base 106. The adhesive layer 104 may include a number of holes formed therethrough, for example, for accommodating lift pins, RF power delivery rod, helium passages and the like. Only exemplary lift pin holes 110 formed in the adhesive layer 104 are illustrated in FIG. 1 for simplicity. The lift pin holes 110 align with lift pin holes 116 formed through the electrostatic puck 102 and lift pin holes 118 formed through the temperature control base 106.
Referring to the partial sectional view of the electrostatic chuck assembly 100 depicted in FIG. 2, the electrostatic puck 102 generally includes a chucking electrode 202 embedded in a dielectric body 204. The dielectric body 204 is typically fabricated from ceramic materials, such as aluminum nitride and/or oxide. The chucking electrode 202 may be a metal mesh or other suitable conductor. Chucking of a substrate (i.e., wafer) placed on the substrate support surface 120 is achieved through Coulombic or Johnsen-Rahbeck effect by applying a DC voltage to the chucking electrode 202 through the RF power delivery rod (not shown) passing through the temperature control base 106 and adhesive layer 104.
The temperature control base 106 generally includes a thermally conductive body 216, typically fabricated from aluminum, stainless steel or other material with good thermal conductivity. At least one temperature control feature 218 may be formed in and/or coupled to the thermally conductive body 216. The temperature control feature 218 may be a heater or chiller, and in the embodiment illustrated in FIG. 2, the temperature control feature 218 is shown as inner and outer channels 220, 222 through which separately controlled heat transfer fluid may be circulated to provide separate temperature control zones across the substrate support surface 120 of the electrostatic puck 102.
During fabrication and/or use of the electrostatic chuck assembly 100, volatiles out-gassed by the adhesive layer 104, particularly during curing, may become trapped between the electrostatic puck 102 and the temperature control base 106. The trapped volatile gases may delaminate the adhesive layer 104 from one or both of the electrostatic puck 102 and the temperature control base 106, such as shown by a void 210 illustrated in FIG. 2. The void 210 increases thermal impedance between the electrostatic puck 102 and the temperature control base 106 which can result in out-of-spec temperature uniformity on the substrate (e.g., wafer) processed, which in turn leads to costly loss of yield and productivity. Further, in applications which utilize moisture-cured silicones as the adhesive layer 104, fully curing the adhesive layer 104 requires adequate presence and availability of moisture locally at the bond site. Adequate moisture availability becomes difficult or impossible when the adhesive layer is very thin relative to the diameter of the adhesive layer resulting in incomplete curing of the adhesive. This further aggravates the likelihood of volatile out-gassing during use and subsequent delamination and/or deteriorating performance of the electrostatic chuck assembly 100.
As the electrostatic chuck assembly 100 must be periodically refurbished, the high aspect ratio of the adhesive layer 104 makes it difficult to thoroughly expose the interior portions of the adhesive layer 104 to solvents needed to efficiently weaken the bond between the electrostatic puck 102 and the temperature control base 106. If the adhesive layer 104 cannot be sufficiently weakened, the electrostatic puck 102 and/or the temperature control base 106 may become damaged if the electrostatic puck 102 and the temperature control base 106 are forcefully pried apart. In extreme instances, the temperature control base 106 may need to be machined away to free the electrostatic puck 102. Thus, refurbishment of conventional electrostatic chuck assemblies 100 may be labor intensive, have high scrap rates and be undesirably expensive.
The above mentioned problems are not unique to electrostatic chuck assemblies, but present to some extent in just about all semiconductor chamber components which utilize a contiguous layer of adhesive to bond two substrates. This problem also exists in display and solar vacuum processing applications as well where the bonding surface areas can be much larger.
Therefore, a need exists for improved methods for bonding substrates, components fabricated by the same, along with improved methods for refurbishing said components.